Fan control circuit

ABSTRACT

A control circuit controls a fan to cool an integrated baseboard management controller (iBMC) in a server. The control circuit includes a state determination module. When the server is powered off and the iBMC is operating, the state determination module receives low level signals from a power supply unit (PSU) and the iBMC. The state determination module connects the PSU and the fan, such that the fan is operating. When the server and the iBMC are powered off, the state determination module receives a low level signal from the PSU and a high level signal from the iBMC. The state determination module disconnects the PSU from the fan, turning the fan off. When the server is operating, the state determination module receives a high level signal from the PSU. The state determination module disconnects the PSU from the fan, turning the fan off.

BACKGROUND

1. Technical Field

The present disclosure relates to a circuit for controlling a fan.

2. Description of Related Art

In current servers, integrated baseboard management controllers (iBMCs)are usually used. However, there are no special fans to cool the iBMCs.This may result in overheating of the iBMCs.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referenceto the following drawing. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the view.

FIG. 1 is a block diagram of an exemplary embodiment of a controlcircuit for a fan.

FIGS. 2-4 are circuit diagrams of the control circuit of FIG. 1.

DETAILED DESCRIPTION

The disclosure, including the accompanying drawings, is illustrated byway of examples and not by way of limitation. It should be noted thatreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 shows an embodiment of a control circuit. The control circuit isto control a fan 2 for cooling an integrated baseboard managementcontroller (iBMC) 1 in a server 100. The control circuit includes atemperature measurement module 10, a state determination module 12, anda speed adjustment module 15.

The state determination module 12 is connected to the iBMC 1 and a powersupply unit (PSU) 16, to determine states of the iBMC 1 and the PSU 16,and outputs corresponding determination signals. The state determinationmodule 12 further supplies power to the fan 2 or does not supply powerto the fan 2 according to the determination result. The statedetermination module 12 is further connected to the temperaturemeasurement module 10 and the speed adjustment module 15. The statedetermination module 12 further supplies power to the temperaturemeasurement module 10 and the speed adjustment module 15 or does notsupply power to the temperature measurement module 10 and the speedadjustment module 15 according to the determination result.

The temperature determination module 10 is further connected to the iBMC1, to measure ambient temperature in the vicinity of the iBMC 1. TheiBMC 1 is further connected to the speed adjustment module 15, to outputcorresponding pulse-width modulation (PWM) signals to the speedadjustment module 15 for controlling the fan 2. In the embodiment, thePSU 16 supplies a standby power signal P3V3_STBY.

Referring to FIGS. 2-4, the state determination module 12 includes an ORgate U5, an inverter U4, and a metal oxide semiconductor field effecttransistor (MOSFET) Q3. A first input terminal of the OR gate U5 isconnected to the iBMC 1 for receiving a state signal BMC_WORK_OK fromthe iBMC 1. A second input terminal of the OR gate U5 is connected tothe PSU 16 for receiving a state signal PWRGD_PS from the PSU 16. Anoutput terminal of the OR gate U5 is connected to an input terminal ofthe inverter U4. An output terminal of the inverter U4 is connected to agate of the MOSFET Q3. A source of the MOSFET Q3 is connected to thestandby power signal P3V3_STBY. A drain of the MOSFET Q3 is to supply apower signal P3V3_S1 to the fan 2 and the temperature measurement module10.

The temperature determination module 10 includes two temperature sensorsU1 and U2. Data pins SDA of the temperature sensors U1 and U2 areconnected to a data pin iBMC_SDA of the iBMC 1 through resistors R5 andR6 respectively. Clock pins SCL of the temperature sensors U1 and U2 areconnected to a clock pin iBMC_SCL of the iBMC 1 through resistors R7 andR8 respectively. Power pins VCC of the temperature sensors U1 and U2 areconnected to the drain of the MOSFET Q3 for receiving the power signalP3V3_S1. An alert pin ALERT of each of the temperature sensors U1 and U2is connected to the drain of the MOSFET Q3 through resistors R9 and R10respectively. An input/output (I/O) pin A0 of each of the temperaturesensors U1 and U2 is grounded through resistors R11 and R12respectively. An I/O pin A1 of each of the temperature sensors U1 and U2is connected to the drain of the MOSFET Q3 through resistors R13 and R14respectively. An I/O pin A2 of each of the temperature sensors U1 and U2is connected to the drain of the MOSFET Q3 through resistors R15 and R16respectively. Ground pins GND of the temperature sensors U1 and U2 aregrounded.

The speed adjustment module 15 includes two bipolar junction transistors(BJTs) Q1 and Q2. A base of the BJT Q2 is connected to the standby powersignal P3V3_STBY through resistors R4 and R3 in that order. A nodebetween the resistors R4 and R3 is connected to a pulse-width modulationpin iBMC_PWM of the iBMC 1. An emitter of the BJT Q2 is grounded. Acollector of the BJT Q2 is connected to the drain of the MOSFET Q3through a resistor R1. The collector of the BJT Q2 is further connectedto a base of the BJT Q1. An emitter of the BJT Q1 is grounded. Acollector of the BJT Q1 is connected to the drain of the MOSFET Q3through a resistor R2. The collector of the BJT Q2 is further connectedto a control pin CTL of the fan 2. A power pin VCC of the fan 2 isconnected to the drain of the MOSFET Q3 for receiving the power signalP3V3_S1. A ground pin GND of the fan 2 is grounded. A sense pin SEN ofthe fan 2 is idle.

When the server 100 is operating, the state signal PWRGD_PS from the PSU16 is at a high level. When the server 100 is powered off, the statesignal PWRGD_PS from the PSU 16 is at a low level. When the iBMC 1 isoperating, the state signal BMC_WORK_OK from the iBMC 1 is at a lowlevel. When the iBMC 1 is powered off, the state signal BMC_WORK_OK fromthe iBMC 1 is at a high level.

In the embodiment, the temperature sensors U1 and U2 are located nearthe iBMC 1 for measuring a temperature of the iBMC 1. Furthermore, thetemperature sensors U1 and U2 have system management bus (SMBUS)interfaces.

When the server 100 is powered off and the iBMC 1 is operating, thestate signal BMC_WORK_OK from the iBMC 1 is at a low level, and thestate signal PWRGD_PS is at a low level. As a result, the input terminalof the inverter U4 receives a low level signal. The MOSFET Q3 is turnedon. The standby power signal P3V3_STBY is transmitted to the temperaturemeasurement module 10 and the fan 2 through the MOSFET Q3. Thetemperature measurement module 10 measures the temperature of the iBMC1, and transmits the temperature of the iBMC 1 to the iBMC 1. The iBMC 1outputs corresponding PWM signals according to the temperature, to thespeed adjustment module 15. The speed adjustment module 15 controls thefan 2 according to the PWM signals.

When the server 100 and the iBMC are powered off, the state signal BMC₁₃WORK_OK from the iBMC 1 is at a high level, and the state signalPWRGD_PS from the PSU 16 is at a low level. As a result, the inputterminal of the inverter U4 receives a high level signal. The MOSFET Q3is turned off. The fan 2 is not operating.

When the server 100 is operating, the state signal PWRGD_PS from the PSU16 is at a high level. In this state, when the iBMC 1 is operating orpowered off, the OR gate U5 outputs a high level signal. The MOSFET Q3is turned off. The fan 2 is powered off. Under this circumstances, theserver 100 is operating, and a system fan (not shown) of the server 100is operating, so the iBMC 1 can be cooled by airflow from the system fanof the server 100. The fan 2 is powered off to save power.

In other embodiments, the speed adjustment module 15 and the temperaturemeasurement module 10 can be omitted. In other words, the controlcircuit can activate or deactivate the fan 2, but cannot adjust thespeed of the fan 2. In addition, the BJTs Q1 and Q2, and the MOSFET Q3function as electronic switches.

The foregoing description of the exemplary embodiments of the disclosurehas been presented only for the purposes of illustration and descriptionand is not intended to be exhaustive or to limit the disclosure to theprecise forms disclosed. Many modifications and variations are possiblein light of disclosure above. The embodiments were chosen and describedin order to explain the principles of the disclosure and their practicalapplication so as to enable others of ordinary skill in the art toutilize the disclosure and various embodiments and with variousmodifications as are suited to the particular use contemplated.Alternative embodiments will become apparent to those of ordinary skillsin the art to which the present disclosure pertains without departingfrom its spirit and scope. Accordingly, the scope of the presentdisclosure is defined by the appended claims rather than the foregoingdescription and the exemplary embodiments described therein.

What is claimed is:
 1. A control circuit set in a server, the controlcircuit controls a fan to cool an integrated baseboard managementcontroller (iBMC) in the server, the control circuit comprising: a statedetermination module connected to the iBMC and a power supply unit (PSU)of the server, for determining states of the iBMC and the PSU; whereinwhen the server is powered off and the iBMC is operating, the statedetermination module receives a low level signal from the PSU and a lowlevel signal from the iBMC, the state determination module connects thePSU and the fan, such that the fan is operating; when the server and theiBMC are powered off, the state determination module receives a lowlevel signal from the PSU and a high level signal from the iBMC, thestate determination module disconnects the PSU from the fan, such thatthe fan is powered off; and when the server is operating, the statedetermination module receives a high level signal from the PSU, thestate determination module disconnects the PSU from the fan, such thatthe fan is powered off.
 2. The control circuit of claim 1, wherein thestate determination module includes an OR gate, an inverter, and a firstelectronic switch, two input terminals of the OR gate are respectivelyconnected to the iBMC and the PSU, for respectively receiving statesignals from the iBMC and the PSU, an output terminal of the OR gate isconnected to an input terminal of the inverter, an output terminal ofthe inverter is connected to a control terminal of the first electronicswitch, a first terminal of the first electronic switch is connected tothe PSU, a second terminal of the first electronic switch is connectedto a power pin of the fan.
 3. The control circuit of claim 2, whereinthe first electronic switch is a field effect transistor (MOSFET), agate of the MOSFET is the control terminal of the first electronicswitch, a source of the MOSFET is the first terminal of the firstelectronic switch, and a drain of the MOSFET is the second terminal ofthe first electronic switch.
 4. The control circuit of claim 1, furthercomprising: a temperature measurement module connected to the iBMC andthe state determination module, wherein when the server is powered off,and the iBMC is operating, the state determination module receives thelow level signal from the PSU and the low level signal from the iBMC,the state determination module further connects the fan and thetemperature measurement module, the temperature measurement modulemeasures a temperature of the iBMC, the iBMC outputs correspondingpulse-width modulation (PWM) signals according to the temperature; and aspeed adjustment module connected to the iBMC and the fan, for adjustingthe fan according to the PWM signals from the iBMC.
 5. The controlcircuit of claim 4, wherein the temperature measurement module comprisesat least one temperature sensor, a data pin of the temperature sensor isconnected to a data pin of the iBMC through a first resistor, a clockpin of the temperature sensor is connected to a clock pin of the iBMCthrough a second resistor, a power pin of the temperature sensor isconnected to the state determination module, an alert pin of thetemperature sensor is connected to the state determination modulethrough a third resistor, first to third input/output pins of thetemperature sensor are connected to the state determination modulethrough fourth to sixth resistors respectively, a ground pin of thetemperature sensor is grounded.
 6. The control circuit of claim 4,wherein the speed adjustment module comprises: a second electronicswitch comprising a control terminal connected to a pulse-widthmodulation pin of the iBMC, a first terminal grounded, and a secondterminal connected to the state determination module through a seventhresistor; and a third electronic switch comprising a control terminalconnected to the second terminal of the second electronic switch, afirst terminal grounded, and a second terminal connected to the statedetermination module through an eighth resistor, and connected to acontrol pin of the fan.
 7. The control circuit of claim 6, wherein thesecond electronic switch is a bipolar junction transistor (BJT), a baseof the BJT is the control terminal of the second electronic switch, acollector of the BJT is the second terminal of the second electronicswitch, and an emitter of the BJT is the first terminal of the secondelectronic switch.
 8. The control circuit of claim 6, wherein the thirdelectronic switch is a bipolar junction transistor (BJT), a base of theBJT is the control terminal of the third electronic switch, a collectorof the BJT is the second terminal of the third electronic switch, and anemitter of the BJT is the first terminal of the third electronic switch.